There are lots of apps offers this feature only for WhatsApp but Parallel Space App is one solution all duplicate apps.
This app creates a virtual space inside your smartphone where your second WhatsApp's gets installed.
Features of this app are :
lightweight : only 2MB in size
RAM friendly : Performance of the app is decent while running on 1gb RAM, If you want to install multiple duplicate apps like 2 Whatsapp,2FB & 2 Gmails then you will need at least 2GB RAM size in your mobile so your mobile os + other apps will smoothly
Free : Currently this app is totally free and you can download directly.
Follow these steps to install and setup.
1. Go to google play, download & Install.
2. This app will require the approval of lots of permission as same as Whatsapp/Facebook.
3.After installation go to app see the image.
4.Now installed WhatsApp or FB or Gmail it will get installed same as normal device.
5.My recommendation is : Only install 2/3 apps WhatsApp & Facebook.